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Physics Unit 3

Key Words from Physics Unit 3

TermDefinition
Ultrasound Sound with a higher frequency than we can hear (above 20 000 Hz).
Refractive Index A measure of how much a substance can refract a light ray.
Critical Angle When the angle of refraction is increased until the refracted ray emerges along the boundary.
Converging Lens A lens that makes light rays parallel to the principal focus converge at a point.
Focal Length The distance from the centre of a lens to the point where light rays parallel to the principal axis are focused.
Real Image An image formed by a lens that can be projected on a screen.
Ciliary Muscles Attached to the lens by suspensory ligaments. The Ciliary muscles change the thickness of the eye lens.
Retina The light sensitive cells around the inside of the eye
Cornea Transparent layer that protects the eye and helps to focus light on to the Retina.
Iris Coloured ring of muscle that controls the amount of light entering the eye.
Pupil The central hole formed by the Iris. Light enters the eye through the Pupil.
Short-sighted When the uncorrected image is formed in front of the Retina instead of on the Retina. The eye muscles can not make the eye lens thin enough. You use a Diverging lens to correct it.
Long-sighted When the uncorrected image is formed behind the Retina. The eye lens can not be made thick enough. You use a Converging lens to correct it.
Lens Power Measured in the Dioptre.
Endoscope Used to see inside the body directly.
Diverging Lens Makes parallel rays spread out.
Virtual Image Formed by a diverging lens and, if the object is nearer to the lens than the principal focus, by a converging lens.
Moment The turning effect of a force.
Charge-coupled Device (CCD) Used to record and display an image.
Total Internal Reflection Occurs when the angle of incidence of a light ray in a transparent substance is greater than the critical angle.
Principle Of Moments For an object to be in equilibrium, the sum of all the clockwise moments about any point must = the sum of the total anti-clockwise moments about that point.
Centre Of Mass The point where an object's mass may be thought to be concentrated.
Centripetal Force The resultant force towards the centre of a circle acting on an object moving in a circular path.
Hydraulic System
Time Period The time taken for one complete cycle of oscillating motion.
Frequency The number of wave crests passing a fixed point every second.
Motor Effect When a current is passed along a wire in a magnetic field and the wire is not parallel to the lines on the magnetic field, a force is exerted on the wire by the magnetic field.
Electromagnetic Induction The process of inducing a potential difference in a wire by moving the wire so it cuts across the lines of a force of a magnetic field.
Near Point Of Human Eye The nearest point to an eye at which an object can be seen in focus by the eye. (Usually 25cm)
Blind Spot
Created by: Charlie360